The present invention relates to a solid golf ball having a cover made of polyurethane resin, which golf ball is endowed with a high rebound, a suitable feel on impact and an excellent durability.
Recently, from an environmental standpoint, the idea of utilizing waste materials by incorporating such materials in golf ball core- or cover-forming materials has begun to emerge in the golf ball industry. The basic characteristics of golf balls include flight performance, feel on impact, and durability. When a waste material is included in the core or cover, it is essential to choose the type and amount of waste material included in such a way as not to markedly worsen these basic properties.
For example, U.S. Pat. No. 6,203,450 describes the compounding of polyurethane rubber in the core material. However, the resulting golf ball can hardly be said to have a suitable feel, and moreover was unable to achieve a reduced spin rate.
Also, golf balls which use a polyurethane material as the cover material instead of the ionomers commonly used to date have become prominent lately. These golf balls with a polyurethane cover are capable of having an improved flight performance on shots with a driver, and also improved controllability owing to increased spin on approach shots.
JP-A 2011-005329 discloses that, by granulating an ionomer resin which was used as a cover material and including the granulated resin in a core-forming rubber composition, it is possible to utilize a waste material while suppressing a decline in ball performance.
However, the foregoing art does not make use of a polyurethane cover. Nor does it achieve improvements in the durability, spin performance and feel of golf balls which have a polyurethane cover and are composed of two or more pieces.